Radio antenna



April 29, 1 947.

1.. HIMMEL ETAL RADIO ANTENKIA Filed June 12, 1943 2 Sheets-Sheet 1 INVEN TORS u'o/v H/MMEL Noam/v FUCHS ATTORNEY April 29, 1947. L, HIMMELETAL 2,419,552

RADIO ANTENNA I Filed June 12, 1943 2 Sheets-Sheet 2' INVENTORS LfON HIMMEL. MORTON Fae/ls ATTORNEY Patented Apr. 29, 1947 RADIO ANTENNALeonHimmel and Morton Fuchs, New York, N. Y.,

assignors to Federal Telephone and Radio Corporation, Newark, N. J acorporation of Delaware Application June 12, 1943, Serial No. 490,570

8 Claims.

This invention relates to radio antennas and in particular to directiveantenna systems for operation at ultra-high frequencies.

An object of the invention is to provide a rigid unitary antennastructure for operation on ultra-high frequency waves.

Another object of the invention is to provide a directional antennastructure for radiating predominantly horizontally polarized waves.

A further object of the invention is to provide a directional antennastructure for horizontally polarized waves having wave energyconcentrated in a horizontal plane.

A still further object of the invention is to provide an antenna systemsuitable for operation with a portable glide path transmitter.

These and other objects and features of the invention will be bestunderstood from the following description of an embodiment thereof andthe illustrations in the accompanying drawings in which Figs. 1 and 2are partially sectionalized plan and elevational views respectively ofthe antenna system of our invention.

Fig. 3 is a sectional view of the antenna structure taken through thesection 3--3 of Fig. 2 and Fig. 4 illustrates a constant intensity fieldpattern in the horizontal plane resulting from radiation from ourantenna structure.

The antenna structure of our invention is particularly useful inconnection with portable in- I strument landing equipment such as isdescribed in U. S. Alford Patent 2,294,882. This patent describes anantenna system for establishing a suitable glide path for the landing ofaircraft in which two antennas are positioned one above the other in amanner such that the field patterns of the two antennas combine toproduce the glide path. Both antennas operate on the same carrierfrequency, but the radiation from each antenna is modulated at its owncharacteristic frequency and produces what is termed an equi-signalglide path. The antenna arrangement of our invention is particularlysatisfactory for'determining one of the field patterns of the glidepath.

In the Alford patent above referred to, the

radiation patterns resulting from each of the antennas disclosed thereinare symmetrical, that is to say, the intensity of the radiated field issubstantially equal in any two opposite directions from either antennastructure. However, the field pattern on one side only of the antennasystemis employed for determining the glide path. The energy radiatedfrom the opposite side of the antenna represents wasted energy, andfurthermore, should there be any obstacles in the field of this energy,reflected radiation therefrom may produce deleterious eifects such asundesired lobes of energy in the field of the desired glide path. Thisproblem of reradiation is very important in connection with portableequipment since an otherwise suitable location for a landing runway maybe rendered unsuitable due to the reflections from objects located onthe far side of the transmitter with respect to the run- Way.

With the antenna structure of our invention, the fieldpattern whichdetermines the glide path extends substantially from one side only ofthe antenna and since there is little or no radiation from the oppositeside, the problem of undesired reflections from objects to the rear ofthe antenna does not exist.

Referring now to Figs. 1 and 2, the reference character 2 represents awooden mast or other supporting means for our antenna structure. Arectangular frame member composed of a spacing member '6 and threetubular members 8, l0 and I2 is supported on the mast 2 by twoclampingdevices I4 and I6. A junction box 18 is positionedbetweenmembers 8 and I0 and another similar junction box 20 is positionedbetween members l0 and i2. The third junction box 22 is positionedbetween the spacing member 6 and the tubular member I2. The spacingmember 6, the tubular members 8, I0 and I2, the junction boxes I8, 20and 22 together with the clamps l4 and it may all be welded or otherwisefastened together to form a very rigid structure. The clamping devicesl4 and I6 are hinged at the points-24 and by operating the clampingscrews 26 and nuts 28 the complete antenna structure maybe readilyfastened to or removed from the mast. The dowel 29 locates the antennastructure on the mast 2.

Two antenna arms 30 and 32 may be welded or otherwise fastened to thejunction box I8 in such a manner that the two arms make an angle witheach other to form a V having an apex substantially coinciding with thecenter line of the tubular member Ii]. Similar antenna arms 34 and 36may be welded or otherwise fastened to the junction box 20 and thesearms also are in clined at a angle to each other to form a V' having anapex substantially coinciding to the tubular member ID. The arms 30 and32 lie in a plane which is parallel to the plane formed by the arms 34and 36. The arms 32 and 36 lie in a plane as do the arms 30 and 34whereby the angle between the arms 38 and 32 is equal to the anglebetween the arms 34 and 36. This angle is not critical but in accordancewith our invention is preferably of the order of 60.

The cover plates 38 and ti! for the junction boxes 20 and I8'respectively are removable for the purpose of assembling sections oftransmission lines within the tubular members. The transmission linesare employed for carrying radio frequency energy to the four antennaarms.

A capacitance element $2 is insulatingly mounted on the divergent end ofeach of the antenna arms. The detail of this construction is shown inFig. l in connection with the antenna arm 32. An insulating spacingmember i l having two reduced portions '55 and 38 is pressed into theantenna arm 32 as illustrated. The insulating member may be composed ofDilectine or other low-loss material. The capacitance element G2 ispressed over the reduced portion 48 of the insulating member 443.

The antenna arm 32 also serves as the outer conductor of a concentrictransmission line comprising said antenna arm and the inner conductortiigthe latter being suitably spaced from the walls of the antenna armby insulating members 52. The conductor 59 is soldered or otherwisefastened to the capacitance element 42. Similar capacitance elements,insulating members, and inner conductors of transmission lines aremounted on and within all of the four antenna arms.

The antenna arms are energized throughthe capacitance coupling whichexists between the capacitance elements and the antenna arms inaccordance with principles disclosed in U. S. Alford Patent 2,287,226.

'Within the tubular member it] is a balanced transmission line composedof two conductors 54 and 5%. Within the junction box iii a connec tionis made between the conductor 54 and the inner conductor 561. Theconductor 50 is very much smaller than the conductor 54, This is rem r ampedan ma n PW SQS since it is desirable that the impedance of thecoaxial line represented by the conductor 5i) and the antenna arm 32 besubstantially equal to twice t e imp dan e f th al d n mission n withinthe tubular member iii. The coaxial line operates as a quarter waveimpedance transfarm Within the junction box [8 a connection is also madebetween the conductor 55 and the transmission line 53, the latterforming the inner conductor of the coaxial line represented by saidinner conductor and the antenna arm 39. Within the junction box 20similar connections are made between the conductors of the balancedtransmission line and the inner conductors of the transmission lineswhose outer conductors are the antenna arms 3% and '36. A section oftransmission line composed of conductors 62 and 64 alsoextends withinthe, tubular memberv I 2 as an extension ofthe transmission line withinthe tubular member ill. The other end of the conductors E2 and 64 meetand are. connected to a pair .of conductors 6i which terminate within aplug and jack arrangement (not shown) within the fitting 6.8. A flexibletransmission line (not shown) connects with the vconductors 66 andextends to a distant point where it is connected to an energy translatorwhich may be either a transmitter or a receiver.

While we have illustrated the means for energizing the antennaarms 30, 32, 3 4, and 36 as comprising awP anqe grHe etw en said rms.

and the elements 42 other means of energization could be employed suchas for example the inductive means illustrated in Fig. 5 of U. S. AlfordPatent 2,287,220.

We have also shown four shielding members 80, mounted over the ends ofthe antenna arms. These shielding members prevent any accumulation ofmoisture, snow, dirt, or other foreign material from depositing on theinsulating members M which might thereby impair the operation of theantenna system. The members may be held in place by any suitable meanssuch as set screws 32 for example.

Reflecting members 10 and 12 are welded or otherwise fastened to thespacing member 6 and to the tubular members 8 and i2 respectively. Thesereflecting members are parasitically excited from the antenna arms towhich they are adjacent,

For a given wave length or frequency, the dimensions of the antennasystem of our invention are substantially as follows: The length of eachof the four antenna arms 38, 32, 34, and 36 is one-quarter wavelength.The length of each of the reflecting members it and i2 is one-halfwavelength. The distance between the apex of the V formed by the antennaarms and the corresponding reflector element is one-quarter wavelength.These dimensions, given in terms of wavelength, are to be considered aselectrical lengths and not necessarily as actual physical lengths. Thisis in accordance with known practice and theory.

The length of the transmission line within the hollow member it isone-half wavelength as determined by the velocity of wave propagationalong the transmission line. This velocity of propagation is somewhatlower than the propagation of electro-magnetic waves in free space.Therefore the distance between the upper and lower V of the antennaarrangement is somewhat less than one-half wavelength. Thecriterionwhich determines the length of this transmission line is thatthe radiated energy from the upper V should be substantially in phasewith the radiated energy from the lower V. This is desirable in orderthat radiated wave energy will be in phase in a horizontal plane. Sincethe transmission line is one-half wavelength long, a cross-over ortransposition of the conductors 54 and is required and this-cross-overcan be made at any point between the apexes of the two Vs. One way ofproducing this. transposition is to relatively. oppositely rotate thetwo ends of the transmission line by Since the wave radiation from theupper V is in phase with the radiation from the lower V and the two Vsare separated substantially onehalf wave length, radiation inv thevertical direction is very low. This radiation would be zero were it notfor the difference in wave propagation alon the transmission linecomposed of conductors 54 and 56 and in free space. Due to lowerdownward radiation, wave reflections from the ground and other objectswhich may be lo.-

cated beneath the antenna structure. are. greatly.

tenna there will generally b e several lobes of adi timia a ert c l. ls.- t, he lower lobe which is usually employed in determining thepattern for a glide path.

While we have described above the princi les of our invention inconnection with specific apparatus, it is to be clearly understood thatthis description is made only by way of example and not as a limitationon the scope of our invention as set forth in the obJects of ourinvention and the following claims.

We claim:

1, A directive antenna system comprising two antenna arms inclined at anangle to each other to form a V, the length of each of said arms beingsubstantially one-quarter wavelength, a linear reflecting elementpositioned adjacent the open end of said V and substantially one-quarterwavelength from the apex of' said V, the length of said reflectingelement being substantially one-half wavelength, all of said lengthsbeing in terms of the operating wavelength of said antenna system, andmeans for energizing said antenna arms, said energizing means comprisingcapacitance elements, one capacitance element being mounted adjacent theopen end of each of said antenna arms, and a transmission line extendingthrough each of said arms and connected to said capacitance element.

2. A directive antenna system in accordance with claim 1 in combinationwith a substantially identical antenna structure as that recited inclaim 1, said structure being positioned substantially one-halfwavelength from said first named antenna, and a section of transmissionline connecting together the transmission lines extending through thearms of each of said Vs for energizing said antennas in phasecoincidence, said transmission line section being substantiallyperpendicular to the planes of said Vs.

3. A directive antenna system in accordance with claim 1 in combinationwith a substantially identical structure as that recited in claim 1,said structure being positioned substantially one-half wavelength fromsaid first named antenna, the plane passing through said reflectingelements being substantially perpendicular to the planes passing throughsaid Vs, and means for energizing the antennas forming said Vs in phasecoincidence. v

4, A directive antenna ystem in accordance with claim 1 in combinationwith a substantially identical antenna structure as that recited inclaim 1, said substantially identical structure being positioned an evenplurality of quarter wavelengths from the first named antenna, the planepassing through said reflecting elements being substantiallyperpendicular to the planes passing through said Vs, and means forenergizing the antennas forming said Vs whereby radiation perpendicularto the planes of said antennas is substantially zero.

5. A directive antenna system comprising a support, said supportdefining a rectangle, two opposite sides of said rectangle being formedof linear members having lengths substantially equal to one quarterwavelength and having a spacing substantially equal to an even pluralityof quarter wavelengths, four antenna arms, each having a lengthsubstantially equal to one-quarter wavelength, .two of said arms beingconnected to one of said sides to define substantially equal angles,therewith said arms forming a V shaped antenna, the two remaining armsbeing connected to the other of said sides to define with said otherside angles equal to said equal angles, two parallel linear reflectingelements connected to said rectangle, said reflecting elements beingperpendicular to said support and having lengths substantially equal toa half wavelength, all of said lengths being in terms of the operatingwavelength of said antenna system, the plane of said rectangle bisectingsaid reflecting elements, and means for energizing said four antennaarms comprising a capacitance element positioned adjacent the divergingends of said arms, and a transmission line passing through at least oneof the members forming the sides of said rectangle and through saidarms, said transmission line being connected to said capacitanceelements.

6. A directive antenna system in accordance with claim 1 wherein theangle between said arms is ubstantially '7. A directive antenna systemcomprising two antenna arms inclined at an angle to each other to form aV, the length of each of said arms being substantially one-quarterwavelength, a linear reflecting element positioned adjacent the open endof said V and substantially one-quarter wavelength from the apex of saidV, the length of said reflecting element being substantially one-halfwavelength, all of said lengths being in terms of the operating wavelength of said antenna system, and means coupled to said antenna armsfor translating energy therewith.

8. A directive antenna system in accordance with claim 7 wherein, saidmeans for translating energy comprises a transmission line and twocapacitance elements, one of said capacitance elements being positionedadjacent the open end of each of said antenna arms, and means forconnecting said capacitance elements to said transmission line.

LEON HIMMEL. MORTON FUCHS.

REFERENCES CITED I The following references are of record in th file ofthis patent:

UNITED STATES PATENTS

